Merge branch 'winh-ajax-users-dropdown' into 'master'

Make .ajax-users-select dropdown consistent

See merge request !13599

app/assets/stylesheets/framework/selects.scss

@@ -267,6 +267,7 @@
 
 // TODO: change global style
 .ajax-project-dropdown,
+.ajax-users-dropdown,
 body[data-page="projects:edit"] #select2-drop,
 body[data-page="projects:new"] #select2-drop,
 body[data-page="projects:merge_requests:edit"] #select2-drop,